If you really saw that kind of text then i'm sure she is lying.

Are you serious? You broke up with her because of that? You should have talked to her first. Some guys are actually like that! If you broke up with her because of the other reasons, that's more plausible. You need to talk to her and get to the bottom of it to be honest.

i would be frank, you might have leaped to fast. the guy might want her back and sent those messages to spite you, cause he knows you might eventually see it. now if she deleted all the messages on her phone, na una go talk say women dey fishy, i tire ohhh

Why r u still asking wen u just said dat u got d hard core evidence?

I don't think you actually loved her like u claim to hv, breaking up with her without being sure if she indeed cheated or not, isn't a sign of true love.

Blunt truth.

extreme:

even as odd as it might sound for a boy to admit it, i really loved her.  

Helllooo?? And when did it become odd to admit u love a girl?. . . if you's not on some ego trip

extreme:

i stumbled on some voice messages of her ex demandin sex n all from her. he actually said somethin bout enjoyin doin it and wantin more.

 Case in point: I have numerous friends who're happily married now. One calculated text msg from me thanking her for some phoney sex romp would cause a major crack in those homes especially if there're fundamental trust issues already.
I think your judgment here was rather rash though I don't blame u so much, some guys I know would've fractured a few bones of hers.

extreme:

she denies it

  Does this mean anything to you?

  What to do:  
 Call her and apologise. I refuse to believe u're 100% a saint yourself.
 Set the conditions as u'd have 'em . . . what u can't take from her (if u'd have her change her # to forestall further incursions by the intruding slowpoke then tell her), what u want from her. . in short communicate.
 Put the past behind u n' give her a clean slate to start with.

 Her actions thereafter will then determine how things progress.

this is wat i will tell you,i had i similar encounter once and this is wat u should do, u guys sit down and let her explain everything,when she is thru, u should listen to ur heart and do wat it tells u to. if ur heart belives her she is right if not ditch her and look for someone new